Drawdown curve and turbulent boundary layer development for chute flow

Abstract

Chutes are spillway channels that convey high-speed water flows from dam overflow structures to the dam toe. Chute computations up to incipient-aerated flow involving a developing boundary layer and an irrotational flow above it are considered herein. The current literature presents a set of isolated works with unrelated approaches for determining both the drawdown curve and the turbulent boundary layer development profile. Professional organizations including ICOLD, IAHR, USBR and USACE have adopted some of these models in their design recommendations. Herein, both the drawdown curve and the boundary layer profile were reconsidered based on these, either using boundary layer theory, empirical relations or backwater approximations. Limitations of each approach are discussed. Based on the comparative results and a complete numerical solution of the boundary layer flow equations, chute flow computations are then simplified and reduced to the use of two explicit equations, facilitating its adoption in engineering practice.